Lexan does NOT filter out UV

[ace3000_1]

So the worst may be at some point you have to replace the piece of polycarb.

Including cheap frensels.........

Trev

[SGSeeker]

Originally posted by skiguy411
Say you put Lexan XL10 in and forgot which side had the UV blocking. What would be the worse that could happen?

I just etched an arrow into the side of it, pointing to the side with the coating

[TaskMaster]

Originally posted by ace3000_1
How do you know the UV stabilisation material doesnt sink to one side when its cooled?

Trev

The additives are fully dispersed in a homogeneous melt by a processing screw and the final product (be it molded, extruded or cast) is cooled to maintain dimensional tolerance in much much much too quick a time for any such migration to occur. Even in the melt state the polycarbonate is very viscous and not prone to allow such migration. I know this through training and personal experience in molding tens of thousands of pounds of polycarbonate with all types of color concentrates and additives.

[TaskMaster]

Originally posted by ace3000_1


Including cheap frensels.........

Trev

Why would you need to replace fresnels because the polycarb was installed with the filter coating on the wrong side? The polycarb would still filter UV, just at the wrong surface resulting in the polycarb itself being exposed to the UV, but nothing after it. I may be missing your point, but I don't agree that you would have to replace those lenses - I still say the worst case scenario is the plastic polycarb may degrade and need to be replaced.

[ace3000_1]

Originally posted by TaskMaster


Why would you need to replace fresnels because the polycarb was installed with the filter coating on the wrong side? The polycarb would still filter UV, just at the wrong surface resulting in the polycarb itself being exposed to the UV, but nothing after it. I may be missing your point, but I don't agree that you would have to replace those lenses - I still say the worst case scenario is the plastic polycarb may degrade and need to be replaced.

With a filter or not, cheap frensels yellow, thats my point. Unless you have frensels that are UV treated (most moddern decent frensels) they will yellow, take a look at an old ohp's frensels.

From having a read around the last hr i havnt found any site that mentions Lexan in any grade to filter UV unless its specially coated, and imo, that costs a wee bit more then $10.95 (add another zero after the 10 for an eyeglass).

Most sites if not all state the exact same as this one:
http://www.polymerplastics.com/transparents_lexan.shtml

UV reststance is not a UV filter, while it may provide some its not a dedicated filter.

Trev

[TaskMaster]

Originally posted by ace3000_1

With a filter or not, cheap frensels yellow, thats my point. Unless you have frensels that are UV treated (most moddern decent frensels) they will yellow, take a look at an old ohp's frensels.

OK, I just wanted to clarify. You quoted my reply stating the worst effect from installing the polycarbonate backwards was having to replace the polycarbonate when you said that. The fresnels yellowing would not be affected by installing the polycarb with either side facing the light source so I guess I was confused why you quoted me.

Originally posted by ace3000_1

From having a read around the last hr i havnt found any site that mentions Lexan in any grade to filter UV unless its specially coated, and imo, that costs a wee bit more then $10.95 (add another zero after the 10 for an eyeglass).


Most sites if not all state the exact same as this one:
http://www.polymerplastics.com/transparents_lexan.shtml

UV reststance is not a UV filter, while it may provide some its not a dedicated filter.

Trev

I would suggest looking up the UV filtering properties of polycarbonate as that is what Lexan is. As I've already stated plain polycarb is indeed a natural UV filter. It will filter the UV spectrum up to 380nm. If you'd like some web sites that mention this, this optical site here states "UV filters are inherent in the following products, polycarbonate, mid and hi-index lens materials, photochromic glass and plastic." This other site has great UV safety info and states, "Polycarbonate lenses block UVA and UVB (up to 380 nm) in the clear form" and discusses how glass and CR-39 (acrylic) lenses need additional coatings to protect against UV.

Polycarb does filter UV but it is degraded while doing so. UV stabilizers and coatings try to prevent or at least minimize this degredation.

[ancorp]

Wow! Trev is back!
So is the Lexan X10 that is sold in Home Depot ok or not?

[TaskMaster]

Yep, it's OK!

Seiously if you doubt it, take it by an optician or eyeglass shop. They always have those UV meters handy and I can't imagine they'd mind showing you... especially if you wear glasses and went to the shop where you bought them.

[Megaman]

At the bottom of this pdf there is a light-transmission diagram for LEXAN. http://www.openart.com.au/cp/products/C/C06a.pdf
It seems to be around 80% transmissive for visible light and blocking uv rather good.

[TaskMaster]

That is a geat quote to sum it up below that chart, "All grades of LEXAN sheet are essentially opaque at all wavelengths below 385 nanometers, making LEXAN sheet excellent for protecting art objects, display merchandise and fabrics from damaging effects of UV light."

And just for reference:

UVA = 315-380 nm
UVB = 290-315 nm